Brad Summer recently took to Facebook to explain that his 7-year-old daughter, Madison, was preyed upon while using Musical.ly, an app that allows users to lip dub music. Despite closely monitoring her tech usage, Summer said he had no idea that there was a messaging component to the app, WPVI-TV reported.

And he was shocked when he saw the messages his daughter started receiving from a person purportedly posing as a 9-year-old named Jessy. Now, Summer is on a mission to warn other parents about what could go wrong if app usage goes unchecked.

“I knew I had to take action,” Summer told US Weekly of his reaction after discovering some disturbing messages.

Summer said his daughter started receiving messages, with “Jessy” purportedly asking her to send nude photos and photos with no shirt. Luckily, the little girl alerted her parents to what was unfolding, and Summer took action, calling authorities to explain what had unfolded.

“First I want to say how proud of our daughter I am and want this to be a warning to your families,” he wrote. “Please, tell your kids to let you know if anyone ever asks something like this, let them know it’s okay to tell you. It has helped us in this situation.”

Summer also said that he knows some will blame him as a parent, but that he didn’t think anything like this would happen. He also noted that his daughter doesn’t have a phone of her own and that she uses the app on one of her parents’ phones while he or his wife is around.

“I guess we were naive in thinking that our daughter was safe on what we thought to be a kid friendly app. We have learned the hard way,” he wrote. “I ask that you not judge us (many still will) but let our experience teach us all.”

Summer said that a detective located the I.P. address and is seeking the person out who sent the message.

It should be noted that Musical.ly says on its website that children under the age of 13 should not be using the app. There is also a warning about the messaging feature on a page specifically designed for parents.